The invention disclosed herein relates to apparatus for planting seedlings, particularly small trees in terrain which is uncultivated and which is likely to include various types of soil and impediments in the soil such as rocks and other hard objects.
In the planting of trees in uncultivated areas, it is desirable to use a self-propelled vehicle which tows or carries a mechanical planting attachment so that the planting of the trees or other seedlings can be performed rapidly and uniformly. Prior art planting machines usually have included a plow or coulter arranged to cut a slice or furrow in the soil and a planting shoe following closely adjacent the plow. The planting shoe usually included a leading wedge shaped edge and a bifurcated following portion which defined an opening in the soil immediately following the cutting edge, and the operator of the machine dropped a seedling into the opening in the soil. A packing element located behind the planting shoe was movable with the planting shoe and engaged the ground to pack the soil around the seedlings. Prior art packing means have included a pair of packing wheels, with each wheel positioned on opposite sides of the furrow in which the seedlings are planted.
In the conventional planting machines as described above, the plow or coulter is usually required to cut a continuous furrow in the earth, and if the plow engages a rock or other hard obstacle in the soil, it may cause the entire planting machine to lift abruptly into the air, which is likely to cause damage to the planting machine and to the worker operating the planting machine. Also, if the plow, planting shoe or any of the other elements of the planting machine should be urged laterally with respect to the towing vehicle, the planting machine is likely to become damaged because of the twisting forces applied thereto.
The use of a pair of packing wheels run along opposite sides of the seedlings to pack the soil adjacent the seedlings usually reduces the height of the soil about the seedlings and frequently tends to expose the upper roots of the seedlings. In those prior art devices where the packing wheels continuously engage the earth, continuous furrows are formed on opposite sides of the row of seedlings, and subsequent rains are likely to cause washouts, further exposing the roots of the seedlings if not completely washing the seedlings from the soil. Also, the packing of the soil downwardly by the packing wheels occasionally causes air pockets to be formed around the lower roots of the seedlings.